1. Field of the Invention
The present invention relates to a digital image processing technique, and more particularly to a method and apparatus for locating objects in a digital image.
2. Description of the Related Art
Face recognition plays an important role in digital image processing techniques concerned with the study and processing of human faces. Face recognition systems can be included in security systems used in identification of people's identities; can help organize media such as photographs that include faces; etc.
When presented with images including people and objects, a known face recognition system identifies where people's faces are located in the images. The face recognition system then selects for processing only the faces of the people in the images. The task of face identification is complicated by non-face areas and objects present in images, as well as by variability in pose, lighting, expression, etc., of people's faces in images. Techniques to localize human faces in images can help a face recognition system identify which areas in an image are relevant. Moreover, techniques to localize human faces in images can be adapted for use in identifying many other types of objects besides faces. For example, such techniques could be used to identify buildings, trees, cars, etc.
A few publications have studied object identification in digital images. One such technique is described in US Patent Application 2002/0136449 A1 entitled “Apparatus and Method for Extracting Object Based on Feature Matching Between Segmented Regions in Images.” The method described in this work extracts an object from an object extraction target image using pixel-based feature matching between the object extraction target image and a query image, which is a reference image of the object. The query and target images are segmented and matched based on features including color and texture. This method, however, is dependent on the existence of a reference image of an object, and in many cases such a reference image is not available.
Another technique for object identification in digital images is described in US Patent Application 2005/0190963 A1 entitled “Target Object Detecting Method, Apparatus, and Program.” The method described in this work detects objects that are known to exist but have not been detected by other standard target object detection processes. A plurality of characteristic target object detecting processes, each corresponding to a predetermined specific characteristic of the target object, is performed to detect the target object. This method, however, uses predetermined characteristics of target objects, which might restrict the detection process and present challenges when presented with objects of variable characteristics, or with objects that do not feature the predetermined characteristics.
A disclosed embodiment of the application addresses these and other issues by utilizing a method and apparatus to estimate the location of a part of an object in a digital image. The method and apparatus use feature value analysis to determine and refine the location estimate of an object part.